BACILLUS DIPHTHERIA 571 



always be made into another pig of the same weight, which has received 

 an injection of antitoxin (at least 250 units) twelve to twenty-four hours 

 previously. Recently Neisser has suggested that the intracutaneous 

 injection of the suspected bacilli may be used for the determination of 

 virulence. This has the advantage of economy, as several tests can be 

 carried out on the same pig. The method as applied by Zingher and 

 Soletsky 17 has been to use the following modification of Neisser's 

 method: Two guinea-pigs of about 250 gr. are used for the test. The 

 abdominal wall is prepared by shaving or plucking out the hair. A 

 twenty-four-hour pure culture on Loeffler's medium is emulsified in 

 20 c.c. of normal salt solution and 0.15 c.c. of this suspension is injected 

 intracutaneously at a corresponding site into each of the two guinea- 

 pigs. One of these animals is given at the same time an intracardial 

 injection of about 250 units of antitoxin, or preferably is prepared by an 

 intraperitoneal injection of antitoxin twenty-four hours before the tests 

 are made. Six cultures may be tested in this way on two animals. 

 Virulent strains produce a definitely circumscribed local infiltrated 

 lesion, which shows superficial necrosis in two to three days. In the 

 control pig the skin remains normal. This method, in the hands of 

 Zingher, gives results parallel to those obtained with the subcutaneous 

 tests. 



Diphtheria Toxin. 18 Animals and man infected with B. diph- 

 therise show evidences of severe systemic disturbances and even organic 

 degenerations, while the microorganism itself can be found in the local 

 lesion only. This fact led even the earliest observers to suspect that, 

 in part at least, the harmful results of such an infection were attrib- 

 utable to a soluble and diffusible poison elaborated by the bacillus. 

 The actual existence of such a poison or toxin was definitely proved by 

 Roux and Yersin 19 in 1889. They demonstrated that broth cultures 

 in which B. diphtheria had been grown for varying periods would 

 remain toxic for guinea-pigs after the organisms themselves had been 

 removed from the culture fluid by filtration through a Chamberland 

 filter. 



METHODS OF PRODUCTION OF DIPHTHERIA TOXIN. While toxin can 

 be produced with almost all of the virulent diphtheria bacilli, there is 

 great variation in the speed and degree of production, dependent upon 

 the strain of organisms employed and upon the ingredients and reac- 



17 Zingher and Soletsky, Jour. Inf. Dis., 1916, xvii, 54. 

 Loefller, Cent. f. Bakt., 1887. 

 19 Roux and Yersin, loc. cti. 



